The present invention relates to an elastic photosensitive layer containing a polymeric binder, which is capable of being laminated and is applied to a preferably flexible support.
From German Auslegeschrift No. 20 64 080 (corresponding to U.S. Pat. No. 3,804,631) it is known to produce printed circuits by means of photosensitive mixtures in the form of compact layers which represent photopolymerizable copying compositions and which are applied to a metallic support or to an intermediate support consisting of plastic film. These layers are rendered insoluble in the areas exposed to light. The layer areas which were not struck by light can, after exposure, be dissolved away by aqueous-alkaline solutions. As the binders, there are employed copolymers of methacrylic acid and at least one alkyl methacrylate in which at least one of the alkyl methacrylates has an alkyl group comprising from 4 to 15 carbon atoms. The elasticity of such layers must be adjusted by the addition of a plasticizer. Furthermore, the production of printed circuits is tied to a process which, due to the photopolymerization, necessitates an undesirably high energy supply.
There are, however, also processes which require lower light energies for the production of printing masters and printed circuits. One of these is, for example, the electrophotographic process. Various electrophotographic layers have been described which are suitable for the production of such articles. They comprise, for example, a photoconductive, polynuclear, carboxylic aromatic as the photoconductor and are used together with an activator and binders, such as a terpolymer composed of 60% of methacrylic acid-n-hexylester, 10% of styrene and 30% of methacrylic acid (German Offenlegungsschrift No. 27 55 851). The layer is applied to the printing plate support in the form of a solution and the solvent is then removed by evaporation. If the support is flexible or elastic, however, layers of this kind are still not up to ultimate requirements with regard to flexibility or elasticity and, additionally, the adhesion offered by them is not good enough for application to an intermediate support, particularly, if the support film is bent or rolled up.
For the production of printing masters and printed circuits by electrophotographic means, it is also known to use a copolymer of styrene and maleic anhydride as the binder (German Offenlegungsschrift No. 27 26 116 and German Offenlegungsschrift No. 25 26 720, corresponding to U.S. Pat. No. 4,063,948). On a flexible support material and in the specified thickness of 5 .mu.m, however, the binder gives merely a brittle layer, the adhesion of which is not too good and which can be transferred with difficulty only by the application of elevated temperatures and pressure. At these temperatures, polyester films used as supports begin to get distorted and this leads to an undesirable formation of streaks and thickness variations in the transferred layers. In addition, it is difficult to decoat transferred layers of this kind, using aqueous-alkaline solutions, in a subsequent process step.
It has become apparent that, although the known binders and/or layers are well-suited for the production of printing plates and printed circuits on rigid supports, they are less suitable where the supports are elastic or flexible and where relatively greater thicknesses of the layers are required.